Liquid crystal display device

ABSTRACT

A column for defining the interval between a TFT substrate and an opposed substrate is formed at a crossing point between a drain line and a scanning line. At the crossing point where the column is formed, the drain line is formed to have a wider width to prevent light leakage. Further, at the crossing point where the column is formed, the scanning line is formed to have a narrower width to prevent increase of capacitance between the drain line and the scanning line. The column is formed at a crossing point corresponding to a specific color, e.g., a blue pixel B, so that a difference in transmittance and in characteristic of thin film transistors due to formation of the column is initially compensated.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority from Japanese applicationJP2008-044247 filed on Feb. 26, 2008, the content of which is herebyincorporated by reference into this application.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid crystal display device, and inparticular to a technique for ensuring an appropriate interval between aTFT substrate and an opposed substrate, using a column-type spacer.

2. Description of the Related Art

In a liquid crystal display device, liquid crystal is filled between aTFT substrate with a pixel electrode and a thin film transistor (TFT)formed thereon and an opposed substrate with a color filter or the likeformed thereon, and the liquid crystal particles are controlled by meansof an electric field to thereby form an image. The interval between theTFT substrate and the opposed substrate is very small, such as of theorder of a few microns. Conventionally, the interval between the TFTsubstrate and the opposed substrate is determined by dispersing plasticbeads and the like. According to this interval setting by dispersingbeads, however, the beads may not be dispersed consistently, and in sucha case the interval between the TFT substrate and the opposed substratemay not be set as predetermined. In addition, the beads may be dispersedon a pixel electrode, which may cause a problem of light leakage in thevicinity of the beads.

Meanwhile, conventionally, in order to fill liquid crystal, the spacebetween the TFT substrate and the opposed substrate is sealed to bevacant, and liquid crystal is injected into the space by utilizingatmospheric pressure. This method, however, takes time to completeinjection of liquid crystal when the interval between the TFT substrateand the opposed substrate is small and the surface of the liquid crystaldisplay is large. As a result, manufacturing throughput is reduced, andmanufacturing cost resultantly increases. In order to address the above,there has been developed a technique, e.g., for applying, by dropping,the required amount of liquid crystal onto a TFT substrate andthereafter forming an opposed substrate to seal the liquid crystalin-between.

As described above, conventionally, the interval between the TFTsubstrate and the opposed substrate is maintained by small beadsdispersed therein. However, according to the above described liquidcrystal dropping method, the dispersed beads may move as the liquidcrystal is dropped, which results in an area with many beads and an areawith only a few beads. This results in an inconsistent interval betweenthe TFT substrate and the opposed substrate, and an inconsistentinterval between the TFT substrate and the opposed substrate in turnresults in a problem of reduced image contrast and/or inconsistentpixels in a liquid crystal display device.

In order to address the above described problem with a case in which theinterval between a TFT substrate and an opposed substrate is setutilizing beads, there is available a technique for defining theinterval between the TFT substrate and the opposed substrate by forminga column on either the TFT substrate or the opposed substrate, asdisclosed in Japanese Patent Laid-open Publication No. Hei 11-84386.

The column for defining the interval between the TFT substrate and theopposed substrate is conventionally formed on the opposed substrate.Specifically, in formation of a column on the opposed substrate, thecolumn is formed such that, after the opposed substrate and the TFTsubstrate are combined to each other, the column abuts on apredetermined position on the TFT substrate. However, should the opposedsubstrate and the TFT substrate be displaced from each other when beingcombined to each other, a column resultantly abuts outside thepredetermined position on the TFT substrate. This may result in a columnformed on a pixel electrode or a column falling on a through-hole formedon a line of the TFT substrate. A column formed on a pixel electroderesults in light leakage due to orientation disturbance in the portionwhere such a column is formed. A column falling on a through-holeresults in an interval not appropriately defined between the TFTsubstrate and the opposed substrate.

Japanese Patent Laid-open Publication No. Hei 11-84386 discloses astructure in which a column is formed on either the opposed substrate orthe TFT substrate in a position on a capacitance line in order toaddress orientation disturbance which would be caused in the vicinity ofthe column, and moreover, the capacitance line is laid extending in therubbing direction of the alignment film. However, the capacitance line,which is essential in the above described structure disclosed inJapanese Patent Laid-open Publication No. Hei 11-84386, reducestransmittance of the liquid crystal display device. In particular, thecapacitance line extending in the rubbing direction of the alignmentfilm, as described in Japanese Patent Laid-open Publication No. Hei11-84386, further reduces the transmittance.

SUMMARY OF THE INVENTION

An object of the present invention is to realize a liquid crystaldisplay device having a structure in which the interval between the TFTsubstrate and the opposed substrate is defined by a column and orientaldisturbance and transmittance reduction due to formation of the columnare suppressed.

In order to attain the above described object, according to one aspectof the present invention, a column for defining the interval between theTFT substrate and the opposed substrate is formed on the TFT substrateat a crossing point between a drain electrode and a scanning line. Thiscolumn is formed at a crossing point between a scanning line and a drainline corresponding to a pixel of a specific color. Further, at acrossing point between a scanning line and a drain line corresponding toa pixel of a specific color, the width of the drain line is formed widerthan that in other positions, while the width of the correspondingscanning line is formed narrower than that in other positions.

According to another aspect of the present invention, at a crossingpoint between a scanning line and a drain line corresponding to a pixelof a specific color, the width of the scanning line is formed wider thanthat in other positions, while the width of the corresponding drain lineis formed narrower than that in other positions. Specifically, thefollowing arrangement is employed.

(1) According to one aspect of the present invention, there is provideda liquid crystal display device having scanning lines extending in alateral direction and aligned in a longitudinal direction, drain linesextending in the longitudinal direction and aligned in the lateraldirection, a TFT substrate having pixels each having a TFT and a pixelelectrode and formed in an area enclosed by the drain line and thescanning line, the pixels constituting a first pixel, a second pixel,and a third pixel, respectively, depending on a color to which therespective pixel corresponds, and being aligned in the lateraldirection, an opposed substrate placed with a predetermined intervalwith respect to the TFT substrate, and liquid crystal enclosed betweenthe TFT substrate and the opposed substrate, wherein a column fordefining the interval between the TFT substrate and the opposedsubstrate is formed at a crossing point between the drain line and thescanning line corresponding to the first pixel, and a width of the drainline is wider at the crossing point where the column is formed than thatof the drain line in another position.(2) In the above described liquid crystal display, at a point where thewidth of the drain line is wider, a width of the scanning line may benarrower than that of the scanning line in another position.(3) In the above described liquid crystal display, a first TFT may beformed at the crossing point between the drain line and the scanningline, where the column is formed, a second TFT may be formed at aposition adjacent to the crossing point between the drain line and thescanning line, where the column is formed, the first TFT and the secondTFT may be electrically connected to each other, and a channel length ofthe first TFT may be shorter than that of the second TFT.(4) In the above described liquid crystal display, a channel length of aTFT formed at a crossing point between the drain line and the scanningline corresponding to the first pixel may be shorter than that of a TFTformed at a crossing point between the drain line and the scanning linecorresponding to the second pixel or the third pixel.(5) In the above described liquid crystal display, the liquid crystaldisplay device may be of an IPS method.(6) According to another aspect of the present invention there isprovided a liquid crystal display device having scanning lines extendingin a lateral direction and aligned in a longitudinal direction, drainlines extending in the longitudinal direction and aligned in the lateraldirection, a TFT substrate having pixels each having a TFT and a pixelelectrode and formed in an area enclosed by the drain line and thescanning line, the pixels constituting a first pixel, a second pixel,and a third pixel, respectively, depending on a color to which therespective pixel corresponds, and being aligned in the lateraldirection, an opposed substrate placed with a predetermined intervalwith respect to the TFT substrate, and liquid crystal enclosed betweenthe TFT substrate and the opposed substrate, wherein a column fordefining the interval between the TFT substrate and the opposedsubstrate is formed at a crossing point between the drain line and thescanning line corresponding to the first pixel, and a width of thescanning line is wider at the crossing point where the column is formedthan that of the scanning line in another position.(7) In the above described liquid crystal display device, at a pointwhere the width of the scanning line is wider, a width of the drain linemay be narrower than that of the drain line in another position.(8) In the above described liquid crystal display device, a first TFTmay be formed at the crossing point between the drain line and thescanning line, where the column is formed, a second TFT may be formed ata position adjacent to the crossing point between the drain line and thescanning line, where the column is formed, the first TFT and the secondTFT may be electrically connected to each other, and a channel length ofthe first TFT may be longer than that of the second TFT.(9) In the above described liquid crystal display device, a channellength of a TFT formed at a crossing point between the drain line andthe scanning line corresponding to the first pixel may be longer thanthat of a TFT formed at a crossing point between the drain line and thescanning line corresponding to the second pixel or the third pixel.(10) In the above described liquid crystal display device, the liquidcrystal display device may be of an IPS method.

According to the present invention, as a column for defining theinterval between a TFT substrate and an opposed substrate is formed onthe TFT substrate side at a crossing point between a scanning line and adrain line, problems due to formation of the column, including reductionof transmittance and light leakage due to orientation disturbance can bereduced. Further, as the width of the drain line is made wider in aposition where the column is formed, the problem of light leakage due toorientation disturbance can be further suppressed. Still further, as thewidth of the scanning line is made narrower in a position where thewidth of the drain line is wider, increase of parasitic capacitance canbe suppressed.

According to the present invention, as the column is formed only at acrossing point between a drain line and a scanning line corresponding toa pixel of a specific color, difference in transmittance orcharacteristics of TFT's can be compensated for through initial setting,so that color inconsistency due to formation of a column can beprevented.

According to the present invention, as a column is formed at a crossingpoint between a drain line and a scanning line and the width of thescanning line is made wider in a position where the column is formedthan that in other positions, light leakage due to orientationdisturbance can be reduced. Further, as the width of the drain line ismade narrower in a position where the width of the scanning line iswider, increase of parasitic capacitance can be suppressed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a TFT substrate according to a firstembodiment;

FIG. 2 is a plan view of an opposed substrate according to the firstembodiment;

FIG. 3 is a cross sectional view along the line III-III in FIG. 1;

FIG. 4 is a cross sectional view along the line IV-IV in FIG. 1;

FIG. 5 is a plan view of a TFT substrate according to a secondembodiment; and

FIG. 6 is a cross sectional view along the line VI-VI in FIG. 5.

DETAILED DESCRIPTION OF THE INVENTION

In the following, embodiments of the present invention will be describedin detail, based on a structure of an actual liquid crystal cell.

First Embodiment

FIG. 1 is a plan view showing a pixel portion of a TFT substrate towhich the present invention is applied; FIG. 2 is a plan view showing anopposed substrate to be combined with the TFT substrate; FIG. 3 is across sectional view along the line III-III shown in FIG. 1; and FIG. 4is a cross sectional view along the line IV-IV shown in FIG. 1.

In FIG. 1, scanning lines 105 extend in the lateral direction and arealigned in the longitudinal direction, and drain lines 107 extend in thelongitudinal direction and are aligned in the lateral direction. An areaenclosed by the scanning line 105 and the drain line 107 constitutes apixel. In FIG. 1, a blue pixel B, a green pixel G, and a red pixel R aresequentially aligned in the lateral direction. A liquid crystal displaydevice according to this embodiment is of a so-called IPS method, andadjusts the amount of light to pass through the liquid crystal byrotating the liquid crystal particle 140 in a direction parallel to thesubstrate.

In FIG. 1, a comb-electrode which constitutes a pixel electrode 113 isprovided inside a pixel enclosed by the scanning line 105 and the drainline 107, and a plane common electrode 111 (not shown) is provided underthe comb-electrode with an insulating film in-between. The commonelectrode 111 is formed on the entire surface on the substrate except acontact hole formed on a line. In the IPS in this embodiment, the liquidcrystal particle 140 is controlled by an electric line of force which isgenerated between the comb-electrode, or the pixel electrode 113, andthe common electrode 111 formed on the entire surface of the substrate.

A constant voltage is supplied to the common electrode 111, while avideo signal is supplied to the pixel electrode 113 via the drain line107. The video signal is supplied by a TFT. In FIG. 1, the portionindicated by the dot line constitutes a semiconductor layer 103. Thesemiconductor layer 103 is formed using poly-Si. A gate line lies underthe semiconductor layer 103 with a gate insulating film 104 in-between,so that the gate line functions as the gate electrode of the TFT. InFIG. 1, the semiconductor layer 103 is formed in an inverted-C shape,and the gate electrode lies under the semiconductor layer 103 at twopoints. As the semiconductor layer 103 above the gate electrodeconstitutes the channel of the TFT, resultantly, two TFT's are formed inseries in each pixel in the structure shown in FIG. 1.

The semiconductor layer 103 is connected to the drain line 107 under thedrain electrode via a first contact hole CH1. That is, in thisembodiment, the drain line 107 functions also as the drain electrode ofthe TFT. The other end of the semiconductor layer 103 iselectrically-conductively connected to the pixel electrode 113 via asecond contact hole CH2, a third contact hole CH3, and a fourth contacthole CH4. Therefore, a video signal from the drain line 107 is suppliedto the pixel electrode 113 via the TFT.

This embodiment is characterized in that a column 130 for defining theinterval between a TFT substrate 100 and an opposed substrate 200 isformed at a position where the scanning line 105 intersects the drainline 107. The plane shape of the column 130 is of an octagon long in thelateral direction, as shown in FIG. 1. In this embodiment, as the column130 is formed on the TFT substrate 100, a problem due to displacement inposition of the column 130 when combining the TFT substrate 100 and theopposed substrate 200 may be less serious, compared to a case in whichthe column 130 is formed on the opposed substrate 200.

In this embodiment, as the column 130 is formed at a crossing pointbetween the scanning line 105 and the drain line 107, deterioration intransmittance can be suppressed. This is because the crossing pointbetween the scanning line 105 and the drain line 107 originally does notpass light through, and is not utilized in image formation due to a TFTpresent in the vicinity of the crossing point.

However, as formation of the column 130 may disturb orientation of theliquid crystal in the vicinity of the column 130, in order to preventthis influence, in this embodiment, the width of the drain line 107 ismade wider in the vicinity of the crossing point with the scanning line105. Specifically, in this embodiment, the width of the drain line 107at the crossing point is double or larger the width of the drain line107 in other positions. Even this arrangement exerts only littleinfluence in terms of reduction of transmittance as the crossing pointbetween the scanning line 105 and the drain line 107 originally does notcontribute to image formation.

As the width of the drain line 107 is wider at the crossing point, thescanning line 105 overlaps the drain line 107 at the crossing point inan increased area. This means increase of parasitic capacitance, whichbrings, e.g., a phenomenon such as increase of a shift voltage or thelike when the concerned TFT shifts from ON to OFF or vice versa. In thisembodiment, in order to suppress increase of parasitic capacitance inthe vicinity of the crossing point, the width of the scanning line 105in the vicinity of the crossing point is made narrower.

In FIG. 1, a red pixel R, a blue pixel B, and a green pixel G arealigned in the lateral direction. As shown in FIG. 1, the column 130 isformed only at a crossing point between the scanning line 105 and thedrain line 107 corresponding to the blue pixel B. In other words, thecolumn 130 is formed at a crossing point where a TFT for controlling theblue pixel B is formed. As the width of the drain line 107 is wider in aposition where the column 130 is formed, the transmittance in theposition may be slightly reduced compared to that in a position withoutthe column 130 and the characteristic of the concerned TFT may becomedifferent from that of other TFT's.

Here, if the column 130 is formed spreading to pixels of three colors,control for color inconsistency or the like is difficult to be properlyachieved. In this embodiment, however, as the column 130 is formed onlyat a crossing point corresponding to the blue pixel B, influence oncolor inconsistency due to formation of the column 130 is prevented. Inthis case, transmittance of the blue pixel B alone may become smallerthan that of the pixels of other colors, and the characteristic of a TFTwhich controls the blue pixel B may become different from that of apixel of another color. This, however; can be addressed through initialsetting for compensation of the characteristic.

In FIG. 1, a crossing point between the scanning line 105 and the drainline 107 corresponding to the blue pixel B appears every three pixelpitch in the lateral direction, and the width of the drain line 107 iswider at all crossing points corresponding to the blue pixel B than thatin other positions. Meanwhile, it is unnecessary to form a column 130 atall crossing points corresponding to the blue pixel B. This is becausepresence of only the number of columns 130 necessary to ensure theinterval between the TFT substrate 100 and the opposed substrate 200 issufficient. In this embodiment, irrespective of the presence or absenceof the column 130, the width of the drain line 107 is made wider at allcrossing points between the scanning line 105 and the drain line 107corresponding to the blue pixels B to thereby maintain regularity tomake it easier to compensate for color inconsistency or the like throughinitial setting.

In FIG. 1, a semiconductor is formed in an inverted C shape, and a gateline lies under the semiconductor with the gate insulating film 104in-between. A portion of the semiconductor which intersects the gateline constitutes the channel portion of a TFT. Therefore, there are twoTFTs in each pixel, namely, a TFT having a channel portion on the drainline 107 and a TFT having a channel in a portion away from the drainline 107.

In FIG. 1, the channel length of a TFT formed on the drain line 107corresponding to the blue pixel B is shorter than that of a TFT formedon the drain line 107 corresponding to the red pixel R or green pixel G.Therefore, the characteristic of a TFT of the blue pixel B resultantlydiffers from that of TFT's of other pixels. As described above, anarrangement in which the characteristic of a TFT related to the bluepixel B alone differs from that of TFT related to other pixels makes itpossible to compensate for the characteristic through initial setting.

FIG. 2 is a plan view of the opposed substrate 200 corresponding to theTFT substrate shown in FIG. 1, viewed from the TFT substrate side. InFIG. 2, “RCF” refers to a red filter; “BCF” refers to a blue filter; and“GCF” refers to a green filter. The respective filters corresponding toa red pixel R, a blue pixel B, and a green pixel G. The filter extendsin stripe in the longitudinal direction of the screen. Therefore, pixelsin the longitudinal direction on the opposed substrate 200 are notdiscriminated from one another.

A light shielding film BM is formed between filters of respectivecolors. The light shielding film BM, which is formed on the opposedsubstrate 200 before forming the color filter, is indicated by the dotline in FIG. 2. The light shielding film BM absorbs external light toenhance contrast of an image. In FIG. 2, the column 130 formed on theTFT substrate 100 abuts on the light shielding film BM at the boundarybetween the red filter and the blue filter and on the color filter. Asdescribed above, with the column 130 abutting on the light shieldingfilm BM on the opposed substrate 200, reduction in transmittance can besuppressed. The TFT substrate 100 shown in FIG. 1 and the opposedsubstrate 200 shown in FIG. 2 are combined to each other and liquidcrystal is enclosed between the TFT substrate 100 and the opposedsubstrate 200, to thereby form a liquid crystal display panel. FIG. 3 isa cross sectional view of the TFT substrate 100 shown in FIG. 1 alongthe line III-III with the TFT substrate 100 and the opposed substrate200 combined to each other. In FIG. 3, on the TFT substrate 100, a firstbase film 101 is formed using SiN, and a second base film 102 is formedthereon, using SiO₂. Both of the first base film 101 and the second basefilm 102 serve to prevent impurities from dispersing from the glasssubstrate into the TFT region.

In FIG. 3, a poly-Si layer is formed as the semiconductor layer 103 onthe second base film 102. The poly-Si layer is formed by initiallyforming a-Si by means of CVD, and then transforming the a-Si intopoly-Si by means of laser annealing. A gate insulating film 104 isformed using SiO₂, covering the semiconductor layer 103.

A MoW film, which constitutes a gate line, is formed, coating the gateinsulating film 104. Al alloy is used when reduction of resistance ofthe gate line is required. Either the gate electrode or the scanningline 105 is patterned at a photo step. In this embodiment, the scanningline 105 also functions as the gate electrode, as shown in FIG. 1. Thesemiconductor layer 103 below the gate electrode constitutes the channelportion of a TFT. In FIG. 3, two gate electrodes are formed. Therefore,two TFTs are formed in FIG. 3.

A gate electrode having a narrower width corresponds to a TFT formed onthe drain line 107, shown in FIG. 1, and a gate electrode having a widerwidth corresponds to a TFT formed apart from the drain line 107. Asshown in FIG. 3, in this embodiment, the channel length of a TFT formedon the drain line 107 is shorter than that of other TFTs. This isbecause the width of the scanning line 105 is narrower at a crossingpoint corresponding to the blue pixel B than that in other positions. Inthis embodiment, the width of the scanning line 105 at the crossingpoint is a half or narrower than that of the scanning line 105 in otherpositions.

An inter-layer insulating film 106 is formed using SiO₂, covering thegate electrode. The inter-layer insulating film 106 insulates the drainline 107 or source electrode 108 from the scanning line 105. Either thedrain line 107 or the source line 108 is formed on the inter-layerinsulating film 106. The drain line 107 and the source electrode 108 areformed simultaneously in the same process. In this embodiment, the drainline 107 serves also as the drain electrode of the TFT.

A contact hole is formed on the inter-layer insulating film 106 and thegate insulating film 104 to connect the drain line 107 or the sourceline 108 and the semiconductor layer 103. In FIG. 3, the drain line 107and the semiconductor layer 103 are connected through the first contacthole CH1, and the source electrode 108 and the semiconductor layer 103are connected through the second contact hole CH2. An inorganicpassivation film 109 is formed, using SiN, covering the drain line 107and the source electrode 108 to protect the TFT.

An organic passivation film 110 is formed on the passivation film. Theorganic passivation film 110 covers a portion of the TFT, which cannotbe covered due to a pin hole or the like formed in the inorganicpassivation film 109 to protect the TFT, and also serves as aplanarization film. Therefore, the organic passivation film 110 isformed as thick as 1 to 3 μm.

After formation of the organic passivation film 110, a third contacthole CH3 and a fourth contact hole CH4 hole for connecting the pixelelectrode 113, to be formed later, and the source electrode 108 of theTFT are formed. The organic passivation film 110 is formed using aphotosensitive resin, and can be patterned without use of photo-resist.Initially, the fourth contact hole CH4 is formed on the organicpassivation film 110, and the third contact hole CH3 is thereafterformed on the inorganic passivation film 109, using the organicpassivation film 110 as a resist.

Thereafter, the common electrode 111 is formed, using ITO, or atransparent conductive film, on the planarized organic passivation film110. The common electrode 111 is formed on the entire surface of theorganic passivation film 110 by means of sputtering or the like, andremains plane except in the vicinity of the contact hole after thepatterning.

A pixel insulating film 112 is formed using SiN, covering the commonelectrode 111. A contact hole for electrically-conductively connectingthe source electrode 108 of the TFT and the pixel electrode 113 isformed on the pixel insulating film 112. Thereafter, the pixel electrode113 is formed using ITO, or a transparent conductive film, on the pixelinsulating film 112. The pixel electrode 113 is formed by spattering ITOonto the entire surface of the pixel insulating film 112, and thenpatterning the ITO into a comb-electrode, as shown in FIG. 1.

FIG. 3 shows a cross section of the comb-electrode. With a voltageapplied to the pixel electrode 113, an electric line of force isgenerated between the pixel electrode 113 and the plane common electrode111, as shown in FIG. 3, which causes the liquid crystal particle 140 torotate, following the electric line of force. According to the IPS (InPlane Switching) method, transmission of light from the backlight iscontrolled by rotating the liquid crystal particle 140 to thereby forman image.

A column 130 is formed, using resin, on the pixel insulating film 112 ina position corresponding to a crossing point between the scanning line105 and the drain line 107. The column 130 is formed by coating thepixel insulating film 112 and the pixel electrode 113 with resign andthen removing unnecessary resin at photo step. Acrylic resin is used asresin. The height of the column 130 corresponds to the interval betweenthe TFT substrate 100 and the opposed substrate 200, being a few μm.

An alignment film 120 is formed using organic material, covering thepixel electrode 113 and the column 130. In order to align the liquidcrystal particles with respect to the alignment film 120, rubbing iscarried out. Rubbing is a process of rubbing the alignment film 120 in aconstant direction, using cloth. However, presence of the column 130 mayleave a portion around the column 130 only insufficiently rubbed. Thisleads to light leakage from the portion.

In this embodiment, however, as the column 130 is formed at a crossingpoint between the scanning line 105 and the drain line 107 and the drainline 107 has a wider width at the crossing point, reduction of contrastdue to light leakage from an insufficiently rubbed portion, if any,around the column 130 is not caused.

In FIG. 3, the opposed substrate 200 is present on the upper side of theTFT substrate 100. A light shielding film BM is initially formed on theopposed substrate 200. The Light shielding film BM fills up the spacebetween the color filters to thereby enhance image contrast. In thisembodiment, a light shielding film BM is formed also on the opposedsubstrate 200 in a position corresponding to where the column 130 isformed, so that light leakage around the column 130 is prevented by thelight shielding film MB as well.

After formation of the light shielding film BM, color filterscorresponding to the respective pixel colors are formed. In FIG. 3, ablue filter is formed. The surface resulted after formation of the colorfilter is convexo-concave, and therefore an overcoat film OC is formedon the color filter for planarization. Then, an alignment film 120 isformed, followed by rubbing to align the liquid crystal particles.

FIG. 3 shows a state in which the TFT substrate 100 and the opposedsubstrate 200, both formed as described above, are combined opposed toeach other with the column 130 in-between, and liquid crystal isenclosed between the TFT substrate 100 and the opposed substrate 200.The interval between the TFT substrate 100 and the opposed substrate 200is defined according to the height of the column 130.

FIG. 4 shows a cross section along the line IV-IV in FIG. 1, of the TFTsubstrate and the opposed substrate 200 combined to each other. FIG. 4is a cross sectional view corresponding to the green pixel G. In FIG. 4,a structure of the TFT substrate 100 is similar to that described withreference to FIG. 3 except that the width of the gate electrode of a TFTformed at a crossing point between the scanning line 105 and the drainline 107 is identical to that of a TFT formed away from the crossingpoint in FIG. 4. This is because, in FIG. 4, the width of the scanningline 105 which constitutes the gate electrode is constant. Therefore,the channel lengths of the two TFT's are identical and longer than thatof a TFT formed at a crossing point where the column 130 is formed,shown in FIG. 3.

In FIG. 4, a structure of the opposed substrate 200 is identical to thatwhich is described with reference to FIG. 3, except that the colorfilter is a green filter. In addition, no column 130 is formed in FIG. 4because a column 130 is formed only at a crossing point between thescanning line 105 and the drain line 107 corresponding to the blue pixelB in this embodiment.

As described above, according to this embodiment, as the column 130 isformed at a crossing point between the scanning line 105 and the drainline 107, light leakage due to orientation disturbance can be prevented.Also, according to this embodiment, the drain line 107 with the column130 formed thereon has a wider width at a crossing point with thescanning line 105 than that in other positions, risk of light leakagecan be further reduced. Also, according to this embodiment, increase ofcapacitance between the gate and the drain can be reduced in an areawhere the width of the drain line 107 is wider, by reducing the width ofthe scanning line 105.

In this embodiment, as the column 130 is formed at a crossing pointbetween the scanning line 105 and the drain line 107 corresponding tothe same color, a problem of color inconsistency or the like can beavoided by compensating for a difference in light transmittance betweena portion with the column 130 formed thereon and a portion without acolumn 130, a difference in characteristic between transistors, and soforth through initial setting.

Second Embodiment

FIG. 5 is a plan view showing a second embodiment of the presentinvention; and FIG. 6 is a cross sectional view along the line VI-VI inFIG. 5. In FIG. 5, a structure in the second embodiment is similar tothat of the first embodiment shown in FIG. 1 except a portion where thescanning line 105 intersects the drain line 107. In FIG. 5, the scanninglines 105 extend in the lateral direction and are aligned in thelongitudinal direction, and the drain lines 107 extend in thelongitudinal direction and are aligned in the lateral direction. Acolumn 130 is formed at a crossing point between the scanning line 105and the drain line 107, similar to the first embodiment.

In FIG. 5, a column 130 is formed at a crossing point between thescanning line 105 and the drain line 107 corresponding to the blue pixelB. In FIG. 5, in order to address light leakage due to insufficientrubbing around the column 130, the scanning line 105 is formed to have awider width at the crossing point than that in other positions.Accordingly, in order to prevent increase of parasitic capacitance ofthe gate electrode and the drain electrode, the drain electrode isformed to have a narrower width than that in other positions.

The gate line has a wider width at a crossing point between the scanningline 105 and the drain line 107 corresponding to the blue pixel B,irrespective of the presence or absence of a column 130. Note that “acrossing point between the scanning line 105 and the drain line 107corresponding to the blue pixel B” refers to a crossing point where aTFT which controls the blue pixel B is formed.

Also in FIG. 5, two TFT's are formed at a crossing point between thescanning line 105 and the drain line 107 and in the vicinity thereof. InFIG. 5, because the width of the gate electrode is wider in a positionwhere the column 130 is formed, that is, at a crossing point between thescanning line 105 and the drain line 107 corresponding to the blue pixelB, the channel length of a TFT formed therein is longer than that of theother TFT's. Meanwhile, the gate electrode widths of two TFT's at acrossing point between the scanning line 105 and the drain line 107corresponding to a pixel of other colors and in the vicinity thereof areidentical, and thus these TFT's have identical channel length.

A structure of the opposed substrate 200 corresponding to the TFTsubstrate 100 shown in FIG. 5 is identical to that shown in FIG. 2. Thatis, according to this embodiment, as the column 130 is formed at acrossing point between the scanning line 105 and the drain line 107,similar to the first embodiment, a structure of the opposed substrate200 is identical to that in the first embodiment.

The TFT substrate 100 shown in FIG. 5 and an opposed substrate 200similar to that which is shown in FIG. 2 are combined to each other, andliquid crystal is enclosed between the TFT substrate 100 and the opposedsubstrate 200, to thereby form a liquid crystal display panel. FIG. 6 isa cross sectional view of the TFT substrate shown in FIG. 5 along theline VI-VI with the TFT substrate and the opposed substrate 200 combinedto each other.

In FIG. 6, a process until formation of the gate insulating film 104 andcoating of a MoW film to be a gate line is identical to that shown inFIG. 3 in the first embodiment. In FIG. 6, a MoW film, which constituteseither the gate electrode or the scanning line 105, is formed, coatingthe gate insulating film 104. Thereafter, either the scanning line 105or the gate electrode is patterned at a photo step. Also in thisembodiment, the scanning line 105 functions also as the gate electrode.

As shown in FIG. 5, as the scanning line 105, which constitutes the gateelectrode, has a wider width at a crossing point between the scanningline 105 and the drain line 107, the gate electrode at the crossingpoint is longer in FIG. 6, and the channel length of the TFT isaccordingly longer. That is, in FIG. 6, the channel length of a TFTformed at a crossing point between the scanning line 105 and the drainline 107 is longer than that of a TFT formed slightly away from thecrossing point between the scanning line 105 and the drain line 107.

Thereafter, an inter-layer insulating film 106 is formed. Note that aprocess thereafter and a structure related to the thereafter process areidentical to that which is described with reference to FIG. 3. Anopposed substrate 200 is formed on the TFT substrate 100, with astructure of the opposed substrate 200 being identical to that which isdescribed with reference to FIG. 3. As a wider scanning line 105 isformed under the column 130 in this embodiment, light leakage due toorientation disturbance, if occurs, in the vicinity of the column 130 isnot caused.

In FIG. 5, no column 130 is formed at a crossing point between thescanning line 105 and the drain line 107 corresponding to a pixel otherthan the blue pixel B. The cross section along the line D-D′ in FIG. 5is a cross section of the TFT portion corresponding to the red pixel R.This cross sectional view is identical to that in FIG. 4, that is, thecross sectional view along the line IV-IV in FIG. 1 in the firstembodiment, with description of the structure not repeated here. Throughcomparison between the TFT formed at a crossing point between thescanning line 105 and the drain line 107 corresponding to the red pixelR, shown in FIG. 4 and the TFT formed at a crossing point between thescanning line 105 and the drain line 107 corresponding to the blue pixelB, shown in FIG. 6, it is known that the channel length of the TFTrelated to the blue pixel B is longer.

Meanwhile, through comparison between the TFT formed at a crossing pointbetween the scanning line 105 and the drain line 107 corresponding tothe red pixel R, shown in FIG. 4, and the TFT formed at a crossing pointbetween the scanning line 105 and the drain line 107 corresponding tothe blue pixel B, shown in FIG. 3, it is known that the channel lengthof the TFT related to the blue pixel B is shorter. This is a significantdifference between the first and second embodiments.

As described above, also in this embodiment, as the column 130 is formedat a crossing point between the scanning line 105 and the drain line107, light leakage due to orientation disturbance can be avoided. Also,according to this embodiment, a portion of the scanning line 105 at across point with the drain line 107, where the column 130 is formed, hasa wider width than that in other positions, risk of light leakage can befurther reduced. Also, in this embodiment, increase of capacitancebetween the gate and the drain can be reduced in a portion where thescanning line 105 has a wider width by reducing the width of the drainline 107.

Also in this embodiment, as the column 130 is formed at a crossing pointbetween the scanning line 105 and the drain line 107 corresponding tothe same color, a problem of color inconsistency or the like can beavoided by compensating for a difference in light transmittance betweena portion with the column 130 formed thereon and a portion without acolumn 130, a difference in characteristic between transistors, and soforth through initial setting.

Although it is described in the first and second embodiments that thecolumn 130 is formed at a crossing point between the scanning line 105and the drain line 107 corresponding to the blue pixel B, obviously, thepresent invention can be similarly applied when the column 130 is formedat a crossing point between the drain line 107 and the scanning line 105corresponding to either one of the red pixel R or the blue pixel B.Also, although it is described in this embodiment that the IPS has astructure in which the upper comb-electrode is the pixel electrode 113and the lower plane electrode is the common electrode 111, the presentinvention can be similarly applied to a structure in which the uppercolumn-electrode is the common electrode 111 and the lower planeelectrode is the pixel electrode 113.

Further, although it is described in the above that the liquid crystaldisplay device is of a so-called IPS method, application of the presentinvention is not limited to the IPS method but the present invention canbe similarly applied to a so-called TN method, a VA method, and thelike.

While there have been described what are at present considered to becertain embodiments of the invention, it will be understood that variousmodifications may be made thereto, and it is intended that the appendedclaims cover all such modifications as fall within the true spirit andscope of the invention.

1. A liquid crystal display device comprising: scanning lines; drainlines; a TFT substrate; an opposed substrate placed with a predeterminedinterval with respect to the TFT substrate; and liquid crystal enclosedbetween the TFT substrate and the opposed substrate; and wherein a widthof one of the drain lines at a crossing point between the drain line andone of the scanning lines is wider than at other portions of the drainline, a width of the one of the scanning lines at the crossing pointbetween the scanning line and the one of the drain lines is narrowerthan at other portions of the scanning line, the TFT substrate includespixels having TFTs and pixel electrodes, the TFTs including: a first TFTformed at the crossing point between the one of the drain lines and theone of the scanning lines, and a second TFT formed at a positionadjacent to the crossing point between the one of the drain lines andthe one of the scanning line, wherein the first TFT and the second TFTare electrically connected to each other and electrically connected tothe one of the scanning lines, and a gate width of the first TFT isnarrower than a gate width of the second TFT.
 2. The liquid crystaldisplay device according to claim 1, wherein the liquid crystal displaydevice is an In Plane Switching type.
 3. A liquid crystal display devicecomprising: scanning lines; drain lines; a TFT substrate; an opposedsubstrate placed with a predetermined interval with respect to the TFTsubstrate; liquid crystal enclosed between the TFT substrate and theopposed substrate; and wherein a width of one of the drain lines at acrossing point between the drain line and one of the scanning lines isnarrower than at other portions of the drain line, a width of one of thescanning lines extending through a crossing point between the scanningline and one of the drain lines is wider than at other portions of thescanning line, the TFT substrate includes pixels having TFTs and pixelelectrodes, the TFTs including: a first TFT formed at the crossing pointbetween the one of the drain lines and the one of the scanning lines,and a second TFT formed at a position adjacent to the crossing pointbetween the one of the drain lines and the one of the scanning line,wherein the first TFT and the second TFT are electrically connected toeach other and electrically connected to the one of the scanning lines,and a gate width of the first TFT is wider than a gate width of thesecond TFT.
 4. The liquid crystal display device according to claim 3,wherein the liquid crystal display device is an In Plane Switching type.